Resistance unit



June 30, 1936. J. L MUVCHER 2,046,129

RESISTANCE UNIT Filed OCI. 4, 1935 WITNESSES ZM @j lNVENTO ATTORN EY Patented June 30, 1936 UNITED STATES PATENT OFFICE 2,046,129 y RESISTANCE. UNIT John J. Mucher, Brooklyn, N. Y. Application october 4, 1935, serial No. 43,613y

This invention relates to resistance units, and has for an object an improved construction wherein the resistance element is enclosed lnvan insulating and also a metal casing.

Another object of the invention is to provide a resistance unit wherein the parts are metal clad and wherein a coating of moisture resistance material has been applied. y

A further and more specific object of the invention is to provide a resistant unit which may have the parts coated with a varnish or other moisture resistant material, and yet leave the re-a sistance wire of the unit properly electrically connected with the respective terminals.

In the accompanying drawlng- Figure l is a plan View of a resistance unit with terminals thereon embodying certain features of Figure 1 on line 3 3, the same being on an en,

larged scale;

Figure 4 is a view similar to Figure 3 but show-l ing the completed resistance unit with its enclosing insulating members, enclosing metal casing` and coating of moisture resistant material;

Figure 5 is a fragmentary View similar to one end of the structure shown in Figure 4, ,but disclosing a slightly modified form of the invention;

Figure 6 is a view similar to Figure 3 but showing a modied form of invention wherein there is provided two longitudinal grooves instead of one;

Figure 7 is a fragmentary view similar to the righthand portion of Figure 3, but showing a modied form of invention wherein two apertures are provided instead of one;

Figure 8 is a fragmentary bottom view similar to the lefthand end of Figure 2 except that the structure has been modified by the omissionvof the groove and the addition of apertures;

Figure 9 is a sectional view through Figure 8 approximately on the line 9 9;

Figure 1D is a view similar to Figure 7, but showing a moded form wherein there is provided a depression rather than a groove.

In forming resistance units heretofore, it has been customary to clamp terminals to a base having resistant wires wound thereon. This wire is usually made from chromium alloy though it may be made from other metal. Where the terminals are clamped in position, the connection is vsatisfactory and remains satisfactory usually for a long time. However, in the'course of time moisture enters even where the wire has been` (Cl. 20L-67) covered with asbestos or other insulating material. This moisture in time disturbs the connection between the resistant wires and the terminals. This disturbance produces what is known` as a noisy connection and aiects in an objection- 5 able way the action of the unit. Also in the metal clad resistance units now on the market the metal casing formed around the resistor or resistant element does not enclose the resistant element sufficiently tightly to prevent the entrance of 10 moisture as there is always an open space left at the edges along the line where the metal is Y folded. Although the insulating jacket within the metal casing seems to cover up these spaces moisture will in the course oi time creep into it and 15 create a path from the resistant element to the casing and from the casing to the ground. In addition to these objections, leakage may develop by reason of the presence of moisture between theterminals of resistant units where terminals are in close proximity to each other. In order to overcome these objections it has been proposed to protect the parts against the action of the moisture by applying` one or more coatings of varnish over the entire element. This may be done by dipping or applying with a brush and after the varnish has been applied it is proposed to subject the coated resistant unit to a drying heat at approximately 250 degrees Fahrenheit. This dries or bakes thevarnish which may be any suitable varnish, as, for instance, a varnish on the market which uses asphalt as a base, though other forms lof varnish may be used. This form of water proong a resistance unit of the metal clad type is satisfactory so far as the moisture is concerned, but unfortunately the varnish creeps in between the resistant wires and the terminals clamped thereto and produces high resistance contact. Tc overcome all of these diiiiculties, namely, the diiculty of the action of moisture and the dimculty of the action of varnish, an improved construction of connection has been provided and illustrated in the accompanying drawlng- Referring to the accompanying drawing by numerals, l indicates a base of any suitable material, for instance a phenol condensation product, and on this base is provided a winding 2 of fine wire which may be of any desired material, as, for instance, chromium alloy wire. `As illustrated in Figure l, there has been provided terminals 3, 4, 5, and 6, terminals 3 and 6 being the respective ends, while terminals 4 and 5 are positioned at desired points intermediate the ends. All of these terminals have their respective extensions 1 and 8 turned over and clamped tightly in place so that if the unit was used -With merely this clamping action to hold thterminals in contact with the: wire it would work satisfactorily. However, if the varnish was applied, thej same would find Aits way beneath the turnedover ends 'I and 8 and almost immediately produce a poor connection in all or most of the terminals. To obviate this condition, base I has been provided with a groove 9, and, if desired, a groove on each edge could be provided without departing from the'spirit of the invention. In addition, the respective bent-over ends or extensions 'I of the respective terminals are each formed with one or more apertures Ill which is directly above or opposite the groove 9. As it is almost impossible to solder chromium alloy wire to metal terminals, the addition of solder around the terminals would be of no effect. However, as the respective apertures I0 are directly opposite the groove 9,' a drop of solder may be placed in vthese-apertures and then melted by having a soldering iron applied thereto. This will cause the solder to ow downwardlyr intothe groove 9 and surround a number of wires of the coil 2 as illustrated by the solder I I in Figure 3. It will benoted that this solder llls the aperture Ill and also lls the groove 9 and a`number of the wires are embedded therein. The characteristic of solder similar to many other metals is to slightlyshrink when it is cold. By reason of this characteristic the solder after it has been melted and flowed in place will chill and will shrink slightly so as to firmly grip the wires embedded therein. This gripping action is sufficient to provide a perfect electrical conta t and also, sufliciently strong and close as to ievent the entrance of varnish between the solder and the wires. As indicated in.Figure 4, the varnish penetrates and contacts with the winding 2 at substantially all points except where these Wires are embedded in the respective lumps of solder Il. As indicated in Figure 4, the "coating I2 is intended to represent the varnish which has-been baked and which covers not only the outside of the unit except the upper end I3 ofthe respective terminals, but passes into and around the insulation I4 and through-the opening I5 where it spreads so as lto'cover winding 2 and even penetrate beneath all the turned-over extensions I and 8 except where the solder Il ispositioned. As heretofore mentioned, one groove-`9 hasbeen ,found to beentirely satisfactory though a groove' yof the wires extending therein so as to provide a good electrical connection and one which can not be penetrated by the varnish. In operation, ordinarily a piece of cold solder anda suitable iluxA is applied to each of the apertures I0, the same being provided in the proper amount 'so that when a soldering iron contacts therewith the solder will melt and ilow as illustratedin Figure 3. As is well known, solder will kow freely only on a solid heated surface and therefore'it will not go beyond the edges of the respective terminalsand onto the adjacent wires` unless the solder is in excessive amount whichi can never happen as a correct amount is always applied .be-y fore the soldering iron is used.

Instead of having a single groove as shown in y Figure 2 of preferred form, two or more grooves might be used, and also an ordinary plain hole for each terminal. In addition, if desired, a depression may be made in the base material on which the wire is Wound. These and other structures may be utilized without departing from the spirit of the invention. In order to `bring outmore clearly how the same inventive idea may be differently'embodied, Figure 6 has been presented and illustrates 9 and 9 which are iden!- tical as shown in Figure 3 except they are on opposite sides of the base I. In this form of invention, there are provided apertures I0 and I0 as the case may be for each of the respective bentover ends 'I- and 8. A solder filling is provided for each aperture above each groove. Instead of having the arrangement as shown in Figures 3 and 6, another arrangement might be used, namel`ythe groove 9 with a pair of apertures I0 and IU'".

: In Figures 8 and 9, it will be observed that the base I is provided with spaced-apertures I6', said apertures being positioned opposite the respective apertures -II) so that solder'or lead may be used, as illustrated in .Figure 9. Suiiicient solder may be used to ll the respective apertures, and, if desired, to extend entirely through base I so as to impinge against and surround the wires on the opposite side as well as the wires on the side of the aperture I0.

A further embodiment is shown`in Figure 10 wherein is provi-ded merely a depression I'I, said depression being opposite the aperture IU so that solder may be applied as heretofore described. In all of thesey forms of invention, the 'action of the solder is the same and produces a good mechanical, as Well as an electrical connection, between the terminal and the resistance wire. This connection is such that varnish can not enter between the solder Vand the wire.

I claim: 1.

1. A resistance unit comprising a base of insulatingmaterial, a wire resistant element wound on the base, a plurality of terminals, each terminal being formed with an upstanding member and a base member having extensions bent over and clamped to the underside of the resistance element and first mentioned base, one of the bent-over extensions of each of said terminals having. an aperture, said ilrst mentioned base having a groove extending opposite said apertures and a lling of solder for each of the apertures, said solder surrounding and embedding certain of the turns of said unit resistance element.

2. A resistance unit, includinga resistance le'- ment formed with an insulating base and winding of resistancelwire, a plurality of terminals carried by.sa.id resistance elementeach of said` terminals having an aperture, said base having `a groove extending beneath each o f said aperf` tures and a lling of solder illing cachot saidv apertures and the groove'adjacent thereto, said respective llings of solder surroundingand embedding cer'tainnf they turns oi said wire for electrically and .mechanically connecting the-wire\ with the respective terminals.

3. A resistance unit, including a yresistance elment having a baseof insulating material anda resistance wreiwound thereon. vand a terminal applied to ysaid base, said terminal having an. aperture therein, said base having-a depression opposite said. aperture and a filling up or soldering filling said aperture and the depression opposite the aperture, said nlling of solder surrounding and embedding certain o! the turns of said wire for electrically connecting the wire with the terminal.

4. A resistance unit, comprising a resistance element having a base and winding a resistance wire thereon, said base having a groove extending longitudinal thereof whereby each turn of said wire extends across the groove, a plurality of terminal members carried by said resistance element and extending across said groove while resting on a number of turns of said wire, each of said terminals having an aperture opposite said groove, a filling of solder fillingl each of the apertures and that portion of said groove adjacent thereto, each of said fillings of solder completely surrounding and embedding a section of a number of turns of said Wire, an insulating covering for said element, said insulating covering also enclosing that part of the terminals which engage said resistance element, a metal sheathing for said insulating covering and a water-prooi' coating for said sheathing said coating penetrating to a position within the insulating covering, and covering all of said resistance ele- 'ments and terminals in contact therewith except the parts of the wiresurrounded and embedded in said solder.

5. A resistance unit, including a resistance element comprising the base and a winding of resistance wire, said base having a notch in one edge into which certain turns of said wire extend, a terminal member positioned so that a part will t over said notch, said part having an aperture opposite said notch and a filling of solder filling said aperture and said notch, said solde'r surrounding and .embedding that portion of said winding which extends into said notch.

6. A resistance unit comprising a piece of insulating material, having a groove in one face thereof, a winding of resistance wire on said base positioned so as to extend across said groove, a terminal with an apertured extension positioned on said base so that said aperture will be positioned opposite said groove, a lling of solder lling said aperture and said groove adjacent the aperture and surround and embed that portion of said wire between said aperture and said groove.

'1. A resistance unit, including a resistance element formed -with an insulating base and a winding of resistance wire, said base being formed with a depressed portion or portions over which the wire extends, a plurality of terminals carried by said resistance element, each terminal Vbeing 5 overlapping part having an aperture and a lling of solder filling each of said apertures and said 10 depressed part or parts adjacent thereto,4 the respective iillings of solder surrounding and embedding certain turns of said Wire for electrically and mechanically connecting the wire with the respective terminals.

- 8. A resistance unit, including a resistance element formed with a rectangular insulating base and a winding of resistance wire thereon extending from one end of the base to the other, a plurality of metallic terminals carried by said resist 20 ance element, each of said terminals having a terminal extension and a base partly surrounding and clamping said resistance element, said insu-- lating base having a groove on one face adjacent each longitudinal edge, the base of the respective 25 terminal overlapping said grooves, said overlapping part for each terminal having an aperture arranged inline with the respective grooves and a illling of solder for each aperture, each of said fillings of solder surrounding and completely em- 30 bedding certain turns of said wire for electrically and mechanically connecting the Wire with the respective terminals.

9. A resistance unit, including a resistance element formed with a rectangular insulating base 35 and a winding of resistance wire thereon, said base having a number of spaced apertures extending therethrough, a terminal for each of said apertures, each of said terminals having a gripping portion gripping said resistance element and 40 overlapping the respective apertures, the over-` lapping parts of said terminals having apertures in line with the apertures in said insulating base and a illling of solder for each of said apertures, said lling of solder completely filling the aper- 45 tures and surrounding and embedding completely short sections of certain turns of said wire for electrically and mechanically connecting the wire with respective terminals.

50 JOHN J. MUCHER. 

